While Microsoft in Mr. Ballmer’s reign as chief executive has yielded the spotlight to more glamorous companies like Apple, Google and Facebook, it still makes some of the biggest money-gushers in the technology business, including its Windows operating system for personal computers and Office applications like Word. Its profit last quarter was nearly $5 billion, compared with $3.2 billion for Google and $6.9 billion for Apple. Anyone who uses a PC to create a résumé or a term paper or to do online banking is more often than not doing so on a machine running Windows.